Final answer:
The Cascadia subduction zone is an example of a convergent boundary between two tectonic plates at an ocean-ocean convergence. The Juan de Fuca plate is being forced beneath the North American plate, creating an ocean trench.
Step-by-step explanation:
The Cascadia subduction zone is an example of convergent boundary between two tectonic plates. In this case, the Juan de Fuca plate is being forced beneath the North American plate. The subduction zone is marked by an ocean trench, which is a depression in the seafloor where the subducting plate bends and descends into the mantle. This type of convergence is known as ocean-ocean convergence, where one oceanic plate subducts beneath another.